On 8/21/07, Ramon Leon <ramon.leon@allresnet.com > wrote:

> Subject: Magritte: adding a condition on the whole object in
> its description
>
> Hello,
>
> I want to add a condition to a Magritte-described object that
> checks the whole object for consistency (and not just a
> single attribute). Is that possible?
>
> Example: Think about creating a workgroup from some of the
> users of your site. The workgroup has a manager. The
> condition is that the manager must be one of the members of
> the workgroup.
>
> I've tried to do this. I have two descriptions on the
> workgroup class side: one for the manager (saying that it can
> be any of the site's users) and one for the users (saying
> that this is a subset of all users). I can add a method
> #description to modify the standard description that is
> assembled from the description* methods on the class side. So
> I tried:
>
>    Workgroup>>description
>     ^super description
>         addCondition: [:workgroup | workgroup users includes:
> workgroup manager]
>         labelled: 'Manager must be a member of the workgroup';
>         yourself
>
> Alas, trying to edit an existing workgroup, I learned that
> the argument of the condition block is a MACheckedMemento, so
> I can't ask it for users.
>
> What would be the best way to have this check everytime the
> work group is edited? Or should I just write the #manager:
> method such that the condition will be satisfied automatically?
>
> Cheers
> Matthias

See
http://onsmalltalk.com/programming/smalltalk/multiple-field-validation-rules
-in-magritte/ to see how to get at the values you're looking for, very
similar situation.

Ramon Leon
http://onsmalltalk.com

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